1. Field of the Invention
This invention relates to the field of storage area networks (SAN). In particular, the invention relates to configuration between redundant fabrics in a SAN.
2. Description of the Related Art
A SAN is an architecture in which remote computer storage devices are attached to servers (hosts) in such a way that, to the operating system of the host, the storage devices appear as locally attached storage.
When designing a SAN, often there will be two or four distinct “fabrics” which provide connectivity between host devices and storage devices. Here, a “fabric” is a given set of fibre channel switches and cables that form the network between the SAN devices. The multiple fabrics provide redundancy as there are multiple connections between each device which reduces the likelihood of loss of connectivity due to hardware failure or cable breakage on the SAN. Typically, each device on the SAN will be connected to at least two fabrics. Importantly, each fabric will usually connect the same set of devices, in the same pattern of zones—the redundant fabrics are symmetric.
By introducing redundant fabrics, the SAN administrator's workload has also multiplied, since a zoning configuration change to one fabric will also need to be made on all the redundant fabrics. This task is error-prone, as the administrator must ensure that they zone the correct ports on each fabric so that each has the same logical configuration i.e. it connects the same set of devices.
When setting up a fabric, an administrator will typically configure one fabric and then have to do an equal amount of work to configure the other one(s) in a similar, but symmetrically different way.
Customers are building large SANs with 1000 or 2000 ports. Managing these types of redundant fabrics is difficult as it involves having to create and validate zoning configurations. Making a mistake in the zoning configuration is likely to lead to an application I/O error on one or more servers when subsequent SAN maintenance is carried out.